U.S. patent number 5,602,464 [Application Number 08/505,939] was granted by the patent office on 1997-02-11 for bidirectional power converter modules, and power system using paralleled modules.
This patent grant is currently assigned to Martin Marietta Corp.. Invention is credited to John D. Bingley, Frank A. Linkowsky.
United States Patent |
5,602,464 |
Linkowsky , et al. |
February 11, 1997 |
Bidirectional power converter modules, and power system using
paralleled modules
Abstract
A bidirectional power converter array has overall voltage
feedback, an error signal generator, and plural bidirectional power
converter modules. Each module of the array includes a series
inductor and local feedback based upon the inductor current. Each
module also has a resistive current sensor, providing wideband
local feedback. A low-pass filter is coupled to the current sensing
resistor to reduce switching noise. The low-pass filter also
reduces the bandwidth of the local feedback signal, so interactions
with the overall feedback occur, which may result in instability. A
winding transformer-coupled to the series inductor generates AC
signal representing high-frequency components of the inductor
current, relatively free of switching noise. The AC current sample
is added to the low-frequency components derived from the resistor
and low-pass filter, to form a low-noise local feedback signal,
with sufficient bandwidth to reduce unwanted interactions with the
overall system feedback. The feedback signals may be currents
summed at a node. The combination of overall voltage feedback which
is converted to local current feedback in each module allows
modules to be paralleled without any adjustments to the system or
to the individual modules.
Inventors: |
Linkowsky; Frank A. (Jamesburg,
NJ), Bingley; John D. (Yardley, PA) |
Assignee: |
Martin Marietta Corp. (East
Windsor, NJ)
|
Family
ID: |
24012502 |
Appl.
No.: |
08/505,939 |
Filed: |
July 24, 1995 |
Current U.S.
Class: |
323/272; 323/224;
323/282; 307/43 |
Current CPC
Class: |
G05F
3/22 (20130101); H02M 3/1582 (20130101) |
Current International
Class: |
G05F
3/22 (20060101); H02M 3/158 (20060101); H02M
3/04 (20060101); G05F 3/08 (20060101); G05F
001/445 () |
Field of
Search: |
;323/222,224,271,272,282,284,285,906 ;307/43 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wong; Peter S.
Assistant Examiner: Han; Y. J.
Attorney, Agent or Firm: Meise; W. H. Berard; C. A. Young;
S. A.
Claims
What is claimed is:
1. A bidirectional paralleled power converter apparatus for
coupling between a first source of direct electrical energy and a
second source of electrical energy, the voltage of said first
source of direct electrical energy being less than the voltage of
said second source of direct electrical energy, said converter
comprising:
a source of power converter apparatus reference voltage;
power converter apparatus error signal generating means including
an output port, and also including a first input port coupled to
said source of power converter apparatus reference voltage and also
including a second input port coupled to receive a sample of power
converter apparatus feedback voltage, for generating, at said
output port of said power converter apparatus error signal
generating means, a power converter apparatus error signal
representative of voltage error;
at least one bidirectional switching power converter, said
bidirectional switching power converter including a first power
port coupled to said first source of direct electrical energy, and
a second power port coupled to said second source of direct
electrical energy, said bidirectional switching power converter
further including a feedback signal input port coupled to said
output port of said power converter apparatus error signal
generating means, said bidirectional switching power converter
further comprising:
(a) inductance means including first and second terminals;
(b) power coupling means coupled to said first and second power
ports and to said first and second terminals of said inductance
means, for, in a first (boost) mode of operation, periodically
coupling said inductance means alternately (i) across said first
power port and (ii) between said first and said second power ports,
for transferring energy from said first source of direct electrical
energy to said second source of direct electrical energy, and for,
in a second (buck) mode of operation, periodically coupling said
inductance means (i) between said first (1) and said second power
port and (ii) across said first power port, for transferring energy
from said second source of direct electrical energy to said first
source of direct electrical energy, and for changing between said
first and second modes of operation under the control of the duty
cycle of a switching control signal;
(c) resistance-type current sensing means serially coupled with
said inductance means, for generating a current representative
voltage representative of the current flowing in said inductance
means;
(d) control means including a first input port, and an output port,
said output port of said control means being coupled to said power
coupling means, and responsive to the sum of currents applied to
said first input port of said control means, for generating said
switching control signal for said power coupling means;
(e) second coupling means coupled to said first input port of said
control means and to said feedback signal input port of said
bidirectional switching power converter, for converting said power
converter apparatus error signal into a power converter apparatus
control current, and for coupling said power converter apparatus
control current to said first input port of said control means;
(f) third coupling means coupled to said resistance-type current
sensing means and to said first input port of said control means,
for converting said current representative voltage representative
of the current flowing in said inductance means into an
inductance-current representative current, and for coupling said
inductance-current representative current to said first input port
of said control means;
whereby switching noise associated with said current-representative
voltage representative of the current flowing in said inductance
means tends to destabilize said bidirectional switching power
converter; said bidirectional switching power converter further
comprising:
(g) low-pass filtering means coupled to said resistance-type
current sensing means, for low-pass filtering said current
representative voltage representative of the current flowing in
said inductance means, to thereby produce a signal representative
of the low frequency components of the current in said inductance
means, and for applying said signal representative of the
low-frequency components of the current in said inductance means to
said first input port of said control means;
which thereby stabilizes said bidirectional switching power
converter, but tends to destabilize said paralleled power converter
apparatus, because the bandwidth of said inductance-current
representative current is less than the bandwidth of said power
converter apparatus error signal; said bidirectional switching
power converter further comprising:
(h) transformer-type current sensing means magnetically coupled to
said inductance means, and coupled to said first input port of said
control means, for generating a high frequency inductor signal
current representative of the high-frequency components of current
flowing in said inductance means, and for coupling said
high-frequency inductor signal current to said first input port of
said control means;
whereby signals representative of both said low-frequency
components and said high-frequency components of said current in
said inductance means are applied to said first port of said
control means, the bandwidth of said bidirectional switching power
converter is increased, and said paralleled power converter
apparatus is thereby stabilized.
2. An apparatus according to claim 1, wherein each of said
bidirectional power converters is in modular form, whereby
additional bidirectional power converter modules may be added to
said bidirectional paralleled power converter apparatus, for
increasing the power-handling capability of said apparatus, by
coupling said first power ports of said bidirectional switching
power converter modules together, coupling said second power ports
of said bidirectional switching power converter modules together,
and coupling said feedback signal input ports of said bidirectional
switching power converter modules together.
3. An apparatus according to claim 1, wherein said first source of
direct electrical energy is a battery, and said second source of
direct electrical energy is a solar panel.
Description
FIELD OF THE INVENTION
This invention relates to bidirectional power converters for
converting power among electrical storage devices and sources, and
more particularly between batteries and solar panels, and
particularly to such converters which are made in a modular form,
and which can be paralleled in an overall feedback loop for
increased power-handling capability.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,143,282, issued Mar. 6, 1979 in the name of Berard,
Jr., et al., describes a bilateral or bidirectional power converter
described as being for use in a spacecraft application, in which a
common inductor is switched under the control of a pulse-width
modulator, so as to operate in a buck mode when coupling power from
a high-voltage electrical source to a low-voltage electrical
source, and to operate in a boost mode when coupling power from the
low-voltage source to the high-voltage source. The increasingly
stringent power requirements being placed upon spacecraft, in
conjunction with reliability and cost considerations, makes it
imperative to find some way to manifest a spacecraft power system
which is at once inexpensive, and capable of operation at widely
varying load levels on different spacecraft.
SUMMARY OF THE INVENTION
A bidirectional power converter assemblage or array includes an
overall voltage feedback, a voltage error signal generator, and one
or more bidirectional power converter modules. Each bidirectional
power converter module of the array includes a series inductor and
local feedback. The local feedback based upon the inductor current,
and each module includes a resistive current sensor, which provides
a wideband feedback signal for the local feedback control. The
bandwidth of the local feedback signal from the resistive current
sensor extends from direct current (DC) to a high frequency. In
order to reduce power bus noise attributable to switching noise
picked up by the resistive current sensor, a low-pass filter is
coupled to the current-sensing resistor, which attenuates the
switching noise at the higher frequencies. However, the low-pass
filter also reduces the bandwidth of the local feedback signal, so
that unwanted interactions with the overall feedback occur, which
may result in instability. A winding is transformer-coupled to the
series inductor, for generating an alternating- current-coupled
(AC) signal representing high-frequency components of the inductor
current, relatively free of switching noise. The
transformer-derived high-frequency components of the current sample
are added to the low-frequency components derived from the resistor
and low-pass filter, to form a low-noise local feedback signal,
with sufficient bandwidth to reduce unwanted interactions with the
overall system feedback.
The bidirectional power converter array or assemblage meets the
requirement for expandability, because only one bidirectional power
module may be used when the electrical load requirements are low,
or a plurality of such modules may be paralleled to meet higher
power requirements. Since each module is identical, it must only be
space-qualified once, thereby reducing the cost of making a power
system of any size for a new spacecraft, and reduces the risk of
error. Since the modules are paralleled, any failure of one module
may be adjusted for by taking that particular module off-line, and
operating with reduced power capability. This in turn further
enhances the reliability of the spacecraft so made.
In a particular embodiment of the invention, the local control is
based upon the sum of feedback signals in the form of currents
applied to a node. In this embodiment, the overall feedback signal
voltage, the resistor-derived and the transformer-derived local
feedback voltages are all converted to corresponding currents
before application to the current node. This form of feedback
allows parallel application of the overall voltage feedback to a
control input port of each individual bidirectional power converter
module, and allows paralleling of the power output ports of the
modules without "current hogging" or uneven distribution of the
load among the individual modules.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified overall block diagram of a bidirectional
power converter array or apparatus, illustrating a plurality of
individual bidirectional power converter modules with paralleled
power ports, and with common overall feedback;
FIG. 2 is a simplified diagram, in block and schematic form, of one
of the bidirectional power converter modules of the arrangement of
FIG. 1;
FIGS. 3a, 3b, and 3c represent the amplitude component of Bode
plots of the response of the DC current loop, the AC current loop,
and the sum of the DC and AC current loops; and
FIG. 4 is a simplified diagram of a portion of the arrangement of
FIG. 2.
DESCRIPTION OF THE INVENTION
FIG. 1 is a simplified overall block diagram of a bidirectional
power control system according to the invention. In FIG. 1, a first
source of electrical energy in the form of a voltage source 12 is
coupled by a power bus 14 across a resistor 20, which may represent
the internal resistance of the source, or which may represent an
external load, such as a spacecraft payload, or the combination of
both. At the right of FIG. 1, a further source 18 of electrical
energy is coupled by a diode 17 and a power bus 15 across a
resistor 21, which represents an external load, or another portion
of an external load, such as a spacecraft payload, or the
combination of both. In one embodiment of the invention, source 18
is a solar panel, and source 12 is a battery.
The voltage of source 12 is always less than the voltage on bus 15.
The voltage of source 18 may be higher than, or less than the
voltage on bus 15. If the power requirements of the loads, and the
maximum amount of power to be transferred between the sources, are
small enough to be handled by a single bidirectional power
converter, the power converter described in the above-mentioned
Berard, Jr. et al. patent will suffice. If a new spacecraft is then
required, however, in which the power requirements are greater than
those of the single power converter, there is no convenient way to
fulfill the requirement, other than producing a new bidirectional
power converter module, and space-qualifying that new module, which
is both expensive and time-consuming. In accordance with the
invention, the flow of electrical energy (power) between sources 12
and 18 is controlled by a bidirectional power converter array or
arrangement illustrated as a block 10. As illustrated in FIG. 1,
bidirectional power converter arrangement 10 includes power ports
22 and 32 connected to buses 15 and 14, respectively, and also
includes a control signal input port 9.sub.1. A feedback path 4 is
coupled between power bus 15 and an inverting (-) input port
6.sub.2 of an error signal generator 6. A source 8 of reference
voltage is coupled to noninverting (+) input port 6.sub.1 of error
signal generator 6. Error signal generator 6 subtracts the current
output voltage from the reference voltage, to generate an error
signal voltage, which is applied over a signal path 9 to control
input port 9.sub.1 of bidirectional power converter arrangement 10.
Bidirectional power converter arrangement 10 contains one or more
bidirectional power converter modules 100, which are designated
100.sub.1, 100.sub.2, . . . 100.sub.n. Each module 100.sub.x, where
the subscript X represents any one of the modules, has its first
power port 1 connected to power port 32 of bidirectional power
converter arrangement 10, whereby the first power ports 1 of all
the bidirectional power converter modules 100.sub.1, 100.sub.2, . .
. 100.sub.n are connected in parallel. Similarly, each module
100.sub.x has its second power port 2 connected to power port 22 of
bidirectional power converter arrangement 10, whereby the second
power ports 2 of all the bidirectional power converter modules
100.sub.1, 100.sub.2, . . . 100.sub.n are connected in
parallel.
If the modules 100.sub.x of the arrangement of FIG. 1, as so far
described, were identical to those of the Berard, Jr. et al.
patent, each module would attempt to regulate the voltage in
accordance with its own internal reference, with the result that
small differences would cause some of the converters to attempt to
supply more than their share of the full load, subjecting them to
excess stress, while other converters would carry little load.
Overall error voltage feedback is provided in the arrangement of
FIG. 1 by a conductor 9.sub.2, which connects the control input
port c of each bidirectional power converter 100.sub.x in parallel
with the other input ports c, and with the control input port
9.sub.1 of bidirectional power converter arrangement 10. While this
provides a common error voltage for all of the bidirectional power
converters 100.sub.1, 100.sub.2, . . . 100.sub.n, the problem of
current hogging is not thereby solved, because of differences in
the output impedances of the individual modules.
FIG. 2 is a simplified diagram, in block and schematic form, of a
module 100.sub.x in accordance with an aspect of the invention.
Elements of FIG. 1 corresponding to those of FIG. 2 are designated
by like reference numerals. In FIG. 1, an inductor 110 has
terminals 110.sub.1 and 110.sub.2. Inductor terminal 110.sub.1 is
connected, by way of a path or bus 14.sub.1, a low-value
current-sensing resistor 112, a further path 14, and power port 1
to source 12. Inductor terminal 110.sub.2 is connected to a
controllable power switch S1, corresponding to the switch of the
above-mentioned Berard, Jr., et al. patent, and switch S1 in turn
is connected to both ground potential and to power port 2.
The arrangement of FIG. 2 also includes a control circuit C1, which
includes a digital pulse-width modulator (PWM) 210, which produces
mutually antiphase gate drive signals on a pair of signal paths
114, for application to the individual switches (not separately
designated) of switch S1. Pulse-width modulator 210, in turn, is
driven by a summing amplifier and integrator 212, which includes an
operational amplifier 214 having its noninverting (+) input
terminal coupled to ground, and also having a capacitor 216 coupled
between its output terminal and its inverting (-) input port, and
an avalanche or Zener diode 218 coupled across the capacitor. The
noninverting input port of summing amplifier and integrator 212 is
designated 116, and, as known, constitutes a virtual ground when
summing amplifier and integrator 212 is connected as illustrated.
The pulse-width of the switching of power switch S1 is responsive
to the sum (or net) of the currents flowing into port 116 from
resistors 118, 126, and 220. When conventional or positive current
tends to flow into port 116, the pulse width of PWM 210 adjusts, in
a manner which tends to operate switch S1 and inductor 110 in a
buck mode, to transfer electrical energy from source 18 to source
12. Similarly, when positive current tends to flow away from port
116 toward resistors 118, 126, and 220, the pulse-width is
readjusted to tend to operate switch S1 and inductor 110 in a boost
mode, to transfer electrical energy from source 12 to source
18.
Current-sensing resistor 112 of FIG. 2 generates a voltage which is
proportional to the instantaneous current flow, which voltage is
therefore representative of the sensed current. Those skilled in
the art know that current and voltage generally occur together, and
that the difference between a "current" source and a "voltage"
source lies in the impedance of the source, with a voltage source
displaying a lower source impedance than a current source; since
resistor 112 has a low resistance, it also has a low impedance and
therefore constitutes a "voltage" source. The
current-representative sense voltage generated by current flow
through resistor 112 is "floating," in that neither end of the
resistor is at a reference voltage level. The floating signal
voltage is [provided with a ground reference] in a block 122, and
applied by way of a port 120 to a resistor 220, which converts the
sensed voltage to a current, and applies the current to port
116.
In operation of the arrangement of FIGS. 1 and 2, system error
voltage is applied over signal paths 9.sub.2 to control voltage
input ports c of each module. Within each module, a resistor 118
converts the system control voltage into a current, and applies the
current to input port 116 of the local control system C1. Summing
amplifier and integrator 212 of each module compares the current
from its resistor 118 with the current from its resistor 220, and
adjusts the pulse-width applied to power switch S1 in a manner
which tends to maintain the voltage at port 116 near ground. This,
in turn, requires that the current through resistor 220 be equal in
magnitude and opposite in sign to the current in resistor 118.
Since the current in resistor 220 is proportional to the current
sensed by sensing resistor 112, which in turn is equal to the
current in inductor 110, the magnitude of the voltage applied to
control input port c of each module directly controls the current
at power ports 1 and 2.
Switching noise in the arrangement of FIG. 2 is attenuated by
capacitors 222 and 224. Nevertheless, current components
attributable to the switching of switch S1 tend to arise, and to
flow through current-sensing resistor 112. These switching noise
components appear in the sensed voltage across resistor 112, and
therefore also appear in the current through resistor 220. The
integrating function of summing amplifier and integrator 212 of
each module tends to attenuate the current components, but
sufficient integration to remove sufficient noise also tends to
reduce the bandwidth of the local (in-module) feedback. This
bandwidth reduction is disadvantageous, because it tends to bring
the bandwidth of the local feedback loop toward the bandwidth of
the overall feedback loop. This, in turn, tends to result in
undesirable interaction among the modules, and can result in
oscillation of the system. It has been found that it is desirable
to have the bandwidth of the local feedback loop about ten or more
times higher than the bandwidth of the overall feedback loop to
minimize these interactions.
According to an aspect of the invention, the local current sense
signal flowing in resistor 220 is low-pass filtered before it is
summed with the overall feedback signal from resistor 118. This is
accomplished by incorporating a low-pass function into block 122.
This low-pass function has a characteristic, in one embodiment of
the invention, which is illustrated by plot 310 of FIG. 3a. The
low-pass function of block 122 of FIG. 2 attenuates switching noise
in the sensed current from resistor 112 before it is summed. The
break-point of the integration function of summing amplifier and
integrator 212 can now be raised to a higher frequency, as a result
of which the response of the local loop to the overall feedback
signal is much faster or improved. However, the bandwidth of the
local loop is still low, with its concomitant problems.
According to a further aspect of the invention, additional current
sensing is provided by a winding 124, which is magnetically coupled
to power inductor 110, to form a transformer. Current flow in
inductor 110 is transformer-coupled to sense winding 124. As known
to those skilled in the art, only alternating components of current
are coupled from inductor 110 to sense winding 124, and DC
components are not so coupled. This characteristic of transformer
coupling results in a transfer function such as that illustrated as
312 in FIG. 3b. The current sensed by winding 124 tends to have low
switching noise, because of the inductive nature of the inductor
and the winding. Thus, the transformer coupling provides sampled
high-frequency or AC components of the current through inductor
110, with relatively small amounts of high-frequency or switching
noise as compared with resistor 112.
The high-frequency components of the current through inductor 110
sensed by transformer-coupled winding 124 are converted into a
corresponding current by a resistor 126, and the current so
converted is applied to current-summing control circuit input port
116, together with the low-frequency components of the sensed
signal from resistor 112. FIG. 3c illustrates as 314 the transfer
function of the combined current sense signals from resistor 112
and transformer-coupled winding 124.
FIG. 4, is a simplified schematic diagram of bidirectional DC
current sense block 122 of FIG. 2, which changes the reference
level of the voltage appearing across resistor 112, and which
includes a low-pass filter function. In FIG. 4, a differential
amplifier designated generally as 410 includes a pair of
transistors 412, with emitters coupled together, and by way of a
resistor to ground. The bases of one of the transistors of pair 412
is fed by a first voltage divider 414, including series-connected
resistors 414a and 414b, connected between conductor 14 and ground.
The other transistor of pair 412 is fed by a second voltage divider
416, including resistors 416c and 416b connected between conductor
14, and ground. Differential amplifier 410 produces an offset
voltage difference across its output conductors 418a and 418b, for
application to an active differential-input low-pass filter 420.
Low-pass filter 420 includes an operational amplifier 422, with a
feedback network 424 extending from its output terminal 120 to its
inverting input terminal. Feedback network 424 includes a resistor
424a which, together with an input resistor, establishes the
low-frequency gain of the filter 420, and a capacitor 424b, in
conjunction with the resistor, established the filter
characteristic 310 of FIG. 3a.
The invention, then, lies in a bidirectional paralleled power
converter apparatus or array (10), which is adapted to be coupled
between a first source of direct electrical energy (12) and a
second source of electrical energy (18), where the voltage of the
first source of direct electrical energy is less than the voltage
of the second source of direct electrical energy. The converter
(10) comprises a source of power converter apparatus reference
voltage (8) and a power converter apparatus error signal generator
(6). The power converter apparatus error signal generator (6)
includes an output port (9), a first input port (6.sub.1) coupled
to the source of power converter apparatus reference voltage (8),
and also includes a second input port (6.sub.2) coupled to receive
a sample of power converter apparatus feedback voltage. The power
converter apparatus error signal generator (6) generates, at its
output port (9), a power converter apparatus error signal
representative of voltage error. The converter apparatus includes
at least one bidirectional switching power converter (100), which
includes a first power port (1) coupled to the first source of
direct electrical energy (12), and a second power port (2) coupled
to the second source of direct electrical energy (18). Each
bidirectional switching power converter (100) further includes a
feedback signal input port (c) coupled to the output port (9) of
the power converter apparatus error signal generator (6). The
bidirectional switching power converter (100) further comprises
(a) a power inductor (110) including first (110.sub.1) and second
(110.sub.2) terminals;
(b) a power coupler (S1, 14.sub.1) coupled to the first (1) and
second (2) power ports and to the first (110.sub.1) and second
(110.sub.2) terminals of the inductor (110), for, in a first
(boost) mode of operation, periodically coupling the inductor (110)
alternately (i) across the first power port (1) and (ii) between
the first (1) and the second (2) power ports, for transferring
energy from the first source of direct electrical energy (12) to
the second source of direct electrical energy (18), and for, in a
second (buck) mode of operation, periodically coupling the inductor
(110) (i) between the first (1) and second (2) power port and (ii)
across the first power port (1), for transferring energy from the
second source of direct electrical energy (18) to the first source
of direct electrical energy (12), and for changing between the
first and second modes of operation under the control of the duty
cycle of a switching control signal;
(c) a resistance-type current sensor (112) serially coupled with
the inductor (110), for generating a current-representative voltage
representative of the current flowing in the inductor (110);
(d) a control arrangement (C.sub.1) including a first input port
(116), and an output port (114), the output port (114) of the
control arrangement (C.sub.1) being coupled to the power coupler
(S1, 14.sub.1), and responsive to the sum of currents applied to
the first (116) input port of the control arrangement (Cl), for
generating the switching control signal for the power coupler
(S1);
(e) a second coupler (118) coupled to the first input port (116) of
the control arrangement (Cl) and to the feedback signal input port
(c) of the bidirectional switching power converter (100), for
converting the power converter apparatus error signal into a power
converter apparatus control current, and for coupling the power
converter apparatus control current to the first input port (116)
of the control arrangement (Cl);
(f) a third coupler (120) coupled to the resistance-type current
sensor (112) and to the first input port (116) of the control
arrangement (Cl), for converting the current-representative voltage
representative of the current flowing in the inductor into an
inductor-current representative current, and for coupling the
inductor-current representative current to the first input port
(116) of the control arrangement (Cl).
As a result of the invention as so far described, switching noise
associated with the current-representative voltage representative
of the current flowing in the power inductor tends to destabilize
the bidirectional switching power converter. The bidirectional
switching power converter (100) further comprises
(g) a low-pass filter (122) coupled to the resistance-type current
sensor (112), for low-pass filtering the current-representative
voltage representative of the current flowing in the inductor, to
thereby produce a signal representative of the low-frequency
components of the current in the inductor, and for applying the
signal representative of the low-frequency components of the
current in the inductor to the first input port (116) of the
control arrangement (Cl).
The addition of the low-pass filter (122) stabilizes the
bidirectional switching power converter, but tends to destabilize
the paralleled power converter apparatus as a whole, because the
bandwidth of the local inductance-current representative current
feedback signal is less than the bandwidth of the power converter
apparatus error signal. Each bidirectional switching power
converter according to the invention further comprises
(h) a transformer-type current sensor (124, 126) magnetically
coupled to the inductor (110), and coupled to the first input port
(116) of the control arrangement (C1), for generating a
high-frequency inductor signal current representative of the
high-frequency components of current flowing in the inductor (110),
and for coupling the high-frequency inductor signal current to the
first input port (116) of the control arrangement (C1).
As a result of this combination, signals representative of both the
low-frequency components and the high-frequency components of the
current in the inductor are applied to the first port of the
control arrangement, the bandwidth of the bidirectional switching
power converter (100) is increased, and the paralleled power
converter apparatus is thereby stabilized.
Other embodiments of the invention will be apparent to those
skilled in the art. For example, a separate current transformer
coupled in series with the power inductor may be used instead of a
winding transformer-coupled to the power inductor. While a
particular arrangement of FETs and diodes has been illustrated as
S1 in FIG. 3, any equivalent arrangement may be used, as for
example a bipolar transistor/diode arrangement, and actively
controlled devices may be used instead of diodes. While particular
frequency characteristics have been described and illustrated in
conjunction with FIGS. 3a, 3b, and 3c, other rolloff frequencies,
and a larger number of poles may be used.
* * * * *